System and safety device for multiple furnaces



Dec. 31, 1963 w. A. RAY 3,115,926

SYSTEM AND SAFETY DEVICE FOR MULTIPLE FURNACES Filed July 15, 1959 2 Sheets-Sheet 1 70 1 /407 L/Gl/T 9 INVENTOR. I W/LL/AM ,4. P4)

Dec. 31, 1963 w. A. RAY 3,115,926

SYSTEM AND SAFETY DEVICE FOR MULTIPLE FURNACES Filed July 15, 1959 2 Sheets-Sheet 2 (GA/7190A MEANS (0/1/5904 MEANS IN V EN TOR.

BY W i fl United States Patent 0 ice 3,115,) 26 SYSTEM AND dAlFE'IlZ DEVICE FOR h IUL'IIIIE FURNAUEE lVillia-m A. Ray, North Hollywood, Ualifl, assignor to General Controls (10., (Glendale, Qalih, a corporation of (California Filed July 15, 1%9, Ser. No. 827,218 '7 Claims. (El. 158-131) The present invention relates to an improved safety system for multiple furnaces supplied from the same fuel source and particularly to a common safety device sensitive to each of the flame-responsive means in a corresponding one of the multiple furnaces.

Oftentimes fuel is supplied from a single source to a plurality of heating units such as multiple fireboxes 0r combustion chambers. Since the fireboxes or combustion chambers are essentially individual units, the same are desirably monitored by a safety device which is sensitive to proper operating conditions in the firebox or combustion chamber; such proper operation condition may be, for example, the presence of a suitable pilot flame.

In accordance with prior practices, an individual thermocouple is associated with a corresponding firebox and the output of each of the thermocouples is applied to a corresponding safety device. This prior practice thus necessitates a separating safety device for each thermocouple. In accordance with an important feature of the present invention each of the thermocouples has its output applied to a single common safety device, thereby providing a simplified system which is less costly, more foolproof and one in which there is produced a pressure drop through only one safety instead of a plurality of safeties as in prior systems.

For these purposes the system incorporates a novel safety device which involves generally a unitary magnetic structure on which is wound a plurality of coils, such coils being energized by a corresponding sensing device such as a thermocouple. The magnetic structure is such that an armature remains in an attracted position when all of i the coils are energized but the force of attraction between the armature and the magnetic structure is insuflicient to maintain the armature in attracted position when the current flowing through only one of such coils falls below a predetermined value.

It is therefore an object of the present invention to provide an improved safety system for multiple furnaces of the character indicated above.

A specific object of the present invention is to provide an improved magnetic structure operating in conjunction with thermocouples and energized with current from each of the thermocouples to maintain an armature in attracted position when each of the thermocouples is properly heated but which functions to allow the armature to be released when only one of such thermocouples is heated insufficiently.

Another object of the present invention is to provide an improved magnetic structure which is instrumental in achieving the new system outlined above.

Another object of the present invention is to provide an improved safety device responsive to a plurality of different conditions for effecting a control operation or indication when only one of such conditions fail to exist satisfactorily.

Another object of the present invention is to provide an improved magnetic structure for these purposes sensitive to a plurality of different conditions and operating such that when one of such conditions fails to exist satisfactorily, both a magnetic unbalance and a mechanical unbalanced condition exist to cause a control element to move with respect to said magnetic structure.

The features of the present invention which are believed Patented Bl, I363 to be novel are set forth with particularity in the appended claims. This invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof, may be best understood by reference to the following description taken in connection with the accompanying drawings in which:

FIGURE 1 is generally a sectional view through a safety control unit embodying features of the present invention.

FIGURE 2 is a sectional view taken substantially on the line 2 2 of FIGURE 1.

FIGURE 3 is a perspective view illustrating the coil and core structure in the device shown in FIGURE 1.

FIGURE 4 is another perspective view illustrating the core structure shown in FIGURE 3.

FIGURE 5 is a perspective view like FIGURE 4 but of a modified core structure arranged to have wound thereon three separate coils instead of two coils as in FIGURE 4.

FiGURE 6 illustrates a multiple furnace system embodying features of the present invention in which the safety device illustrated in FIGURE 1 is incorporated.

FIGURES 7 and 8 are generally enlarged sectional views illustrating the coaction between the movable armature and the core structure in the device shown in FIG- URE 1; and FIGURE 8 illustrates the manner in which the armature may move with respect to the core structure when one of the multiple coils is de-energized.

FIGURE 9 is generally a sectional View taken in the direction indicated by the arrows in FIGURE 3.

FIGURE 10 illustrates schematically electrical, magnetic and mechanical relationships of elements shown in the previous figures.

FIGURE 11 illustrates another modified structure in which the center leg 55A is flared instead of straight as in FIGURE 10.

The system shown in FIGURE 6, for purposes of simplicity, is illustrated as including only two fireboxes or furnaces 1t and 11, each supplied with fuel-in this case gas. The gas is applied to the inlet 12 of the safety control valve indicated generally at I3. This control valve 13 is shown in detail in FIGURE 1 and actually incorporates many diiferent valves, such valves being the valve 14 defined by the valve seat 15 and its cooperating movable valve element in; and the plug valve element 18 which controls the flow of fuel to the pilot burner outlet 19 and the main burner outlet Ztl. It will be seen that the valve 15, 16, when closed, prevents the flow of fuel to the outlets l9 and Eli regardless of the position of the plug valve element 13. For this purpose the valve l5, i6 is referred to as a safety valve and is controlled both manually and electrically as described in detail later.

The pilot outlet 1% supplies gas to each of the pilot burners MA and 11A in the furnaces 1d and 1 1 respectively. The main burner outlet Z-tl is in communication with the main burners IiltlB and MB in the furnaces lit? and ill. The flow of gases to such main burners lltlB and 118 may be controlled by condition responsive or control means indicated generally at 1M) and 11C respectively, and such condition responsive means may be responsive to various conditions such as, for example, temperature inside furnaces or temperature of a medium heated as a result of the fuel burned by the corresponding main burners. For purposes of simplicity, such condition responsive means are indicated generally as block diagrams in FIGURE 1 since it is well understood by those having knowledge of the art that such condition responsive means may take many different forms for many different purposes in accomplishing this general function of controlling the flow of gas to the burners.

Each one of tie pilot burners Ill-A and HA has associated therewith a suitable flame responsive means for indicating the presence of the corresponding flame from tr e pilot burners; and as illustrated herein, such means comprises a corresponding thermocouple D and 11D heated by the corresponding pilot flame. The thermocouple IltlD is connected to the coil 22 (FIGURES 1, 3, 9) of the magnetic structure 24; and the thermocouple MD is connected to the coil 23 also wound on the same magnetic structure 24 so that current flows through these windings or coils 22 and 23 when corresponding thermocouples idD and 1113 are heated.

The construction of this magnetic structure 24, which includes the armature 25, comprises an important aspect of the present invention and is described in detail in connection with subsequent figures. This armature 25 cooperates magnetically with the stationary core structure 26 on which the aforementioned coils 2-2 and 23 are wound.

The armature 25, generally in the form of a disc, is loosely mounted on the pin 28 which carries the movable valve element 16 and which is slidably mounted in the wall 3t? of housing 31. This armature 25 is normally biased downwardly in FTGURE 1 by the coil compression spring 32 which has one of its ends bearing against the stationary casing wall 3d and the other one of its ends bearing against the valve gasket retainer 34. This pin or stem 28 may be moved upwardly in FIGURE I manually by an operator using his finger to press the button 28A upwardly.

The operation of the system shown in FIGURE 1 is briefly as follows. In the shut down condition of the system the main safety valve 15, I6 is closed and the plug valve element 18 is in a position to disestablish communication between the passage 36 on the One hand and the outlet openings 19 and 2-1 on the other hand. This corresponds to the so-called or position of the manually operable knob 33 for positioning the plug valve element 13. In starting up the system, the knob 38 is rotated to a pilot on position wherein the passageway 36 is placed in communication with the pilot opening 19, and the button 28A is pressed upwardly to open the valve '15, I6 and to move the armature 25 into engagement with the core structure 26, in which case gas then flows in turn from the inlet opening 12, through the valve 15, I6 and through the opening 19 to both of the pilot burners 10A and 11A in the individual furnaces It), 111. The button 28A is maintained manually in its upper position while the gas escaping from the pilot burners ltlA, 11A is ignited and for a time suficiently long thereafter to heat the associated thermocouples 19D, MD, in which latter case the armature 25 is maintained magnetically by the core structure 26 Without requirement of further manual effort.

When this condition is achieved, the operator may release the button 23A and the armature 25 remains retained against the core structure 26 to continue to maintain the valve 15, 16 open. As long as the pilot flames in furnaces ill, ill continue to burn, they are, of course, effective to maintain the valve 15', -16 open and to ignite any gas escaping from the associated main burners MB, 118 in response to one of many various conditions. Should, for any reason, there be a failure in one of the pilot flames, the associated thermocouple 143A, lltiE cools down to a point where the core structure 26 is no longer efiective to maintain the valve l5, 16 open, in which case this valve 15, 16 closes to thereby prevent the flow of gas to either one of the furnaces it), it. It should be carefully noted that the operation is such that the valve 15, 16 closes upon the extinguishment of only one pilot flame. A subsequent resetting operation involving manual operation of the button 23A as outlined above involves relighting of the two pilot burners.

As described in more etail later, the core structure 26 is such that it develops sui'icient magnetic forces to maintain the armature '35 against such core structure only when both of the coils Z2 and are fully energized.

The desirability for shutting down both furnaces 1'9, 11 upon pilot burner failure in only one of the furnaces is quite evident upon consideration of the fact that both furnaces it, it are usually vented to the same stack and that unburned gases flowing into said stack are apt to produce undesirable conditions and perhaps a minor explosion.

The device shown in FIGURE 1 incorporates means illustrated in FIGURE 2 for adjusting the size of the pilot flame. The means illustrated in FIGURE 2 is considered conventional and comprises simply an adjustable plug as threaded in a bore ll to provide an adjustable restriction between the passageways 42 and 43 in the valve body 44, such passages leading to the pilot outlet port 19. Once the adjustable restricting plug 449 is adjusted, the cover 45' in the form of a screw-threaded plug is threaded in the bore 41 with a sealing gasl'et between the cover 35 and the valve casing 44.

After the pilot burners function to maintain the armature 25 in its attracted position, the manual reset button 28A may then be released and the armature 25 will be maintained in its attracted position in engagement with the core 25 notwithstanding the action of the coil compression spring Ell which tends to move the armature 25 from its attracted position.

It will be understood that the reset mechanism involving the reset knob 28A is such that the knob 23A may return to its position shown in FEGURE 1 while the armature 25 is being maintained magnetically against the core Further, it will be understood that the normal physical space between the armature 2:3 and the core 26 as shown in FIGURE 1 is such that the magnetism developed by the coils 22 and 23 (assuming that they are both fully energized) is insufiicient to cause the armature to be moved upwardly to its attracted position, but some manual effort is required to move the armature 25 to its attracted position. For this purpose, of course, tn manually operable knob 23A is provided to allow the operator to move the armature 25 into engagement with the magnetizable core 26 against which the same is retained in attracted position only when both coils Z2 and 23 are and remain properly energized.

After the armature 25 is thus magnetically retained against the core 26, the knob 38 is rotated to its burner on position (in which position the gas is allowed to escape also to the pilot burners MBA and 11A), in which case the passageways as and 23 are then opened to allow the escape of gas to the main burners provided, of course, that the condition responsive or control means ltlC and 11C (FIGURE 6) are in condition to allow flow to th burners. Any gas escaping at any time from the main burners is ignited by the pilot flame. The knob 38 also has an off position and when the knob 38 is rotated to such position, the rotatable valve member 18 prevents flow of gas from the passageway 36 to both outlets 19 and 26), in which case the pilot burners are extinguished. the thermocouples cool sufficiently to allow the armature 2.5 to move to its non-attracted position, and thus the safety valve 14 returns to its closed position illustrated in FIGURE 1. The system may be placed in operation again, as explained above, using and requiring the manual reset operation which involves the application of manual force to the knob 28A to initially move the armature against the core 26.

The present invention, of course, is not limited to furnaces since it is clear that other uses may be made of the same as, for example, in a gas range in which one burner may be in a broiler unit and another burner may be in an oven unit, where one can be ignited from the other resulting possibly in an explosion.

Also, the invention may be used on certain main burners, for example, the larger commercial type where a single pilot is insufiicient to insure ignition and where dolayed ignition may possibly result in explosion. Thus, the present invention is particularly useful where two pilotburners are in use in a common combustion chamber and where it is desired to monitor operation of both pilot burners to insure reliability and fast ignition. Indeed, the present invention may be used in systems of this type where two output signals developed as, for example, by thermocouples, serve to control one common operating unit; and, indeed, instead of the common operating unit being operated from a thermocouple, the control or output signals may be derived from other sources. For example, a single device in accordance with the present teachings and structures incorporated herein may be operated by simultaneous application of output signals from two diilerent electronic amplifiers which respond to the measurement of different physical conditions.

in accomplishing these functions, the structure of the electromagnetic means and particularly the core structure 26, its cooperating armature 25 as well as the mechanical mounting of such armature 2-5 is considered quite important.

The core in FIGURES 1, 3, 4 and 9 is illustrated as being generally cylindrical with two parallel open-ended slots 5@ and machined in the same, the slots terminating a distance from the base to define two arcuate end legs 53 and E54 (around which corresponding preformed coils 22 and 23 are subsequently placed), a center leg 55 and a disc-shaped base portion 56.

The armature 25 is in the form of a disc having substantially the same diamter as core 26, and the abutting surfaces of such armature 25 and legs 53, 5d and 55 are preferably optically ground to assure a good even and uniform contact surface between the same.

The coils 22 and 2-3 are formed from insulated wire and, if desired, additional insulation in the fom of insulation strips so, 61, 62, 223, 6d and as may be used to insulatedly space the wire comprising the coils from the magnetizable core 26. T his cylindrical core 26 may be stationarily mounted as shown in FlGURE 1 using a bolt 7 threaded into a central apertured portion 71 of the core member 26.

The armature 1 .5, in the form of an apcrtured disc, is loosely mounted on the pin 72 which is secured in stem 28 with a bowed dished spring washer '76 between stem 28 and armature to normally maintain the same as shown in FlGURE 7 with the countersunk surface 74 of arma ture 2S mating with a like conical surface defining the head of the pin This means that the armature 25 may rock or pivot as shown in FIGURE 8 with respect to its retaining pin 72 and with respect to the core as to achieve certain advantages described later.

t 13 coils are phased so as to produce magnetic fields in aiding relationship as indicated by the arrows and lift in FiGURE 1 there being one coil for each ALI.) as shown in FIGURE ll).

ln cross section as illustrated in FlGURE 10, the magnetic core is generally Est-shaped with windings 22, 23 cod on outer legs 53, 5d. In the attracted position as "strated, the windings and 233 are fully energized by thermocouples MED, 11D and center leg Ed is considered to carry a relativel small amount of magnetic ilux since one of its ends is, of course, integrally formed with the base portion and the other one of its ends is in engagement with the armature 2 5 through an intimate optically ground contact. in other words, substantially all of the tiny: is considered to how through a path which includes, in turn, leg 5d, base leg 53 and armature 25, returning to leg with little flux passing through center leg d5 since the rnagnetomotive force between the ends of such leg 55 under this condition is substantially equal to zero. Tie magnetic circuit described above is considered to at all times be operated along a substantially linear portion oi its magnetization curve, i.e. in a region below the conventional knee in such curve, where magnetic saturation conditions do not exist.

The magnetic or mechanical pull in such instance may be represented by the equation where P equals the pull in pounds per square inch, B is the flux density in thousands of magnetic lines per square inch and in this instance is substantially directly proportional to the current flowing in coils 22. and 23. These coils 2?. and 23 have the same number of turns and thus produce the same number of ampere turns of flux in legs 53 and 5'4 which are of substantially identical cross-sectional area to achieve the same value of B in each leg 53, whereby the pull on opposite ends of the armature (in FIGURE 16) and more accurately the pull on the disc 25 is substantially uniform along that peripheral portion thereof which engages the legs 53, 5'4.

The armature 25, to remain in its attracted position against the force of compression spring 32, requires this simultaneous or joint energization of coils 22. and 23 in equal amounts; otherwise, the armature 25 is pulled away from its attracted position by the prestressed spring 32, the force of which is applied centrally to the armature disc through a loose or semi-loose connection which allows pivotal movement of such armature as indicated in PEG- URE 8.

Thus, should one winding or 23 be tie-energized or the current flow thcrethrough drop an appreciable amount as, for example, when its corresponding thermocouple ltll) or MD stops generating a suilicient volta e due, for example, to pilot flame outage, then a magnetic unbalanced condition results and the armature moves away from its attracted position. This unbalanced magnetic condition is now described on the assumption that the current flow through winding 22 has lessened a suliicient amount. When this occurs, the magnetomotive force across the ends of leg becomes smaller and thus approaches the same value of magnetomotive force across the ends of the center leg 55 with the result that more of the flux developed by the other winding now flows through the center leg 55 and a lesser amount flows through leg 53. The pull between leg 53 and the adjacent contacting portion of armature 2d lessens more than proportionally since the pull varies as the square of the flux density in accordance with the above formula. Thus, not only is the flux density lessened in the still active leg but also there is a diversion of that iiux produced in leg 54 and flowing into legs 53, such that unbalanced forces with respect to the center of disc exist on disc 93S. This unbalanced force also aids in liberation of the armaturc from its attracted position, i.e. there is less likelihood that the armature will stick to the magnetizable core recause of the existence of such unbalanced forces and the loose or semi-loose mounting of the armature on stem 28 which permits the armature to pivot as indicated in PE"- URE 8 in response to such unbalanced force. This action results in much like a pr ing action in which the armature is pried away from its n agnetizzable core instead of all parts thereof being moved simultaneously equal distances from such core. v'hile it is preferred to take full advantage of such unbalanced forces by thus pivo-tally mounting the armature, in some instances there may be a rigid connection between the armature and its stem.

Using the principles and teachings herein, the attraction of the armature may be controlled in accordance with the failure of one pilot flame in a group of more than two pilot flames. Thus, instead of only forming two coil cores 53 and :55 as in FIGURE 4, the core structure may be formed with three coil cores 9%, and 92 and a central core 93 having an equilateral triangular cross section. in accordance with the above teachings it is understood, of course, that the cross-sectional areas of each leg 9%, 91 and ar the same and that separate coils each having the same number of turns are placed on corresponding legs and that each coil is connected to a separate source of voltage exemplified above in the form of a thermocouple. The core of FIGURE has associated therewith an armature mounted as in H6- l and the operation and functioning is substantially as described above to achieve the result that diminution of current flow through. one of the plurality of coils below a certain level results in movement of the armature from its attracted position by a prestressed coil spring acting on a central portion of the disc armature.

in the three-coil arrangement these coils are phased as before, i.e. to produce flux which aids or flows in the same direction as that produced by the other coils.

in each case it is preferred, as sh Wn in the drawings, t the cross-sectional area of the center leg, i.e. leg 55 in FIGURE 4 or leg in 5, be larger than the crosssectional area of any one of the corresponding coilcarrying outer legs so that a greater diversion of llux results when the current through one of the coils is decreased. Preferably the core material in each instance is of the type having a relatively high initial magnetic permeability, i.e. a high permeability at the smallest current levels.

in some cases it may be desirable to shape the center leg as illustrated, for example, in FIGURE ll by flaring the same outwardly in the direction of the armature, i.e. by making its cross-sectional area progressively larger the closer the same is to the armature. By doing so, the value of B is decreased and also the flux tends to be tangential to the plane of the armature instead of strictly perpendicular to the same, all of which has the effect of reducing the magnetic pull.

While the particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

1 claim:

1. A device of the character described for controlling multiple devices, each having associated therewith a condition-responsive device comprising a single magnetizable core having a plurality of windings thereon, each connectable to a corresponding one of said condition-responsive devices, said core comprising a pair of outer legs and a center leg with a corresponding Winding on a corresponding one of said outer legs, an armature engageable with both of said outer legs and with said center leg in the attracted position of said armature, means biasing said armature away from said core, said biasing means applying a bias' force to said armature at a central point thereon corresponding generally to the axis of said center leg, each of said indings being adapted to be connected to its corresponding condition-responsive device so as to produce a magnetic llux that traverses both of said outer legs with the flux so produced by one of said windings being in series-aiding relationship to the flux so produced by the other of said windings in each of said outer legs.

2. A device as set forth in claim 1 in which said armature is tiitably mounted with respect to said core at a point which is substantial y in the center of the armature.

3. A device of the character described comprising a generally cylindrical core structure having formed therein outer legs and a center leg, separate windings on the corresponding one of said outer legs, the cross-sectional area of said outer legs being substantially the same and the number of turns of each of said windings being substantially the same, the cross-sectional area of said center leg being greater than the cross-sectional area of either one of said outer legs, an armature in the form of a disc having a diameter substantially equal to the diameter of said core and movable into attracted engagement with both said outer legs and said center leg, a stem having its axis extending generally as a prolongation of tne axis of said center leg, means loosely mounting said armature on said stem for pivotal movement of said armature on said stern, means applying a biasing force to said stem in such a direction as to tend to move said armature away from its integrally attracted position, separate sources of current connected to corresponding ones of said windings and serving to maintain said armature in attracted position when e ch of said sources is effective, the attraction be 1g smaller than the force exerted by said biasing means when only one of said current sources is rendered ineffective, each of said windings being connected to its corresponding source so as to produce a magnetic flux that traverses both of said outer legs with the lux so produced by one of said windings being in series-aiding relationship to the flux so produced by the other of said windings in each of said outer legs.

4. In a device of the character described, a core structure comprisin a pair of outer legs and a center leg, a separate Winding on each of said outer legs, a separate current source connected to a corresponding one of said windings, an armature attracted by said core structure and maintained in attracted position against said pair of outer legs and said center leg when each of said current sources is fully effective, means biasing said armature away from said core structure, and said core structure tunctioning to produce a force less than the force exerted by said biasing means when only one of said current sources is rendered ineffective, each of said windings being connected to its corresponding source so as to produce a magnetic flux that traverses both of said outer legs with the flux so produced by one of said windings being in series-aiding relationship to the flux so produced by the other of said windings in each of said outer legs.

5. A device as set forth in claim 4 in which said armaure is pivotally mounted at a point corresponding generally to the center of said center leg and the force exerted by said biasing means is applied to the center of said armature.

6. in a multiple safety system of the character described, a single manually resettable valve means for controlling the llow of fuel to a pair of burners, each of said burners being associated with a thermocouple, an electromagnetic structure incorporating a single magnetizable core and a single armature movable relative thereto, means interconnecting said valve means and functioning to maintain said valve means in an operating position only when said armature is maintained in attracted relationship to said core, a plurality of coils wound on said core for energizing the same, said armature being maintained in attracted position only when all of said coils are energized, means for separately connectim each of said coils to a corresponding one of said thermocouples, and means movably mounting said armature such that the some may pivot on said core structure, said single core having a pair of outer legs and a center leg, one of each of said plurality of coils being wound on a corresponding one of said outer le s, each of said coils being connected to its corresponding thermocouple so as to produce a magnetic flux that traverses both of said outer legs with the flux so produced by one or" said coils being in series-aiding relationship to the flux so produced by the other of said coils in each of said outer legs.

7. In a multiple safety system of the character described, a single manually resettable valve means for controlling the flow of fuel to a pair of burners, each of said burners being associated t n a thermocouple, an electromagnetic structure incorporating a single magnctizable core and a single armature movable relative thereto, means interconnecting said valve means and functioning to maintain said valve means in an operating position only when said armature is maintained in attracted relationship to said core, a plurality of coils wound on said core for energizing the same, said armature being maintained in attracted position only when all of said coils are energized, means for separately connecting each of said coils to a corresponding one of said thermocouples, and a valveactuating element and means for loosely mounting said armature on said valve-actuating element such that the same may pivot on said core when one of said coils is de-energized, said single core having a pair of outer legs and a center leg, one of each of said plurality of coils being wound on a corresponding one of said outer legs, each of said coils being connected to its corresponding thermocouple so as to produce a magnetic flux that traverses both of said outer legs with the flux so produced by one of said coils being in series-aiding relationship to the fiux so produced by the other of said coils in each of said outer legs.

References Cited in the file of this patent UNITED STATES PATENTS Snavely et al Apr. 2, OHagan Oct. 15, Mansky Dec. 19, Mantz Apr. 23, Paille Oct. 20, Thornbery et al J an. 25, Stone Feb. 5, Mathews Apr. 24, Thornbery Feb. 18, Mathews Feb. 10, Wasson Mar. 3, Dietz Apr. 7, Thornbery July 26, Hajny Nov. 8,

FOREIGN PATENTS France May 4,

France May 6, 

1. A DEVICE OF THE CHARACTER DESCRIBED FOR CONTROLLING MULTIPLE DEVICES, EACH HAVING ASSOCIATED THEREWITH A CONDITION-RESPONSIVE DEVICE COMPRISING A SINGLE MAGNETIZABLE CORE HAVING A PLURALITY OF WINDINGS THEREON, EACH CONNECTABLE TO A CORRESPONDING ONE OF SAID CONDITION-RESPONSIVE DEVICES, SAID CORE COMPRISING A PAIR OF OUTER LEGS AND A CENTER LEG WITH A CORRESPONDING WINDING ON A CORRESPONDING ONE OF SAID OUTER LEGS, AN ARMATURE ENGAGEABLE WITH BOTH OF SAID OUTER LEGS AND WITH SAID CENTER LEG IN THE ATTRACTED POSITION OF SAID ARMATURE, MEANS BIASING SAID ARMATURE AWAY FROM SAID CORE, SAID BIASING MEANS APPLYING A BIASING FORCE TO SAID ARMATURE AT A CENTRAL POINT THEREON CORRESPONDING GENERALLY TO THE AXIS OF SAID CENTER LEG, EACH OF SAID WINDINGS BEING ADAPTED TO BE CONNECTED TO ITS CORRESPONDING CONDITION-RESPONSIVE DEVICE SO AS TO PRODUCE A MAGNETIC FLUX THAT TRAVERSES BOTH OF SAID OUTER LEGS WITH THE FLUX SO PRODUCED BY ONE OF SAID WINDINGS BEING IN SERIES-AIDING RELATIONSHIP TO THE FLUX SO PRODUCED BY THE OTHER OF SAID WINDINGS IN EACH OF SAID OUTER LEGS. 